1. Field of the Invention
The-present invention relates to a method for arranging a plurality of cells when they are combined in use, and also relates to an assembled battery arranged by using the arranging method.
2. Description of the Related Art
When arranging a plurality of cells in use, the cells have been arranged so as to be perpendicular to the surface on which they are disposed. The space where the cells are disposed has been limited, for example, to a quite small space due to the demand for improving the spatial efficiency. For example, in an electric car, cells are in most cases disposed under the floor in order to secure an accommodation space and a luggage space sufficiently. In this case, in order to secure the required minimum height of the floor of a vehicle, sufficient height of a space for disposing the cells can not be obtained in the actual state. In view of such a fact, the height of the cells is required to be as low as possible. Further, the shape and the size of the space in which the cells are disposed differs at every manufacturing company of the electric car and at every type of a car. Thus, the cell is designed so as to have a size suitable for the space to be disposed at every manufacturing company and at every type of a car, and then the cells thus designed are manufactured and mounted in the car.
However, at the time of disposing cells, since the size of each cell is newly designed in accordance with the space in which the cells are disposed, it is difficult to mass-produce the cells, and much time and effort is required. Thus, there arises a problem that the cost of the cell increases and the cells can not be supplied quickly in response to the demand.
Accordingly, it is an object of the present invention to provide a method for disposing cells in a limited space without using a process of changing the design of the cell and to provide an assembled battery which can be disposed in such a space.
In a method for arranging a plurality of cells of an elliptic cylindrical shape for solving the aforesaid problem, each of the cells of an elliptic cylindrical shape includes
(1) a lid wall; and
(2) a main body of a cell casing having a side wall and a bottom wall opposing to the lid wall, wherein
(3) each of the lid wall and the bottom wall is configured in a substantially elliptic shape having a major axis A, a minor axis B and arc or elliptic arc portions at both ends of the major axis, and
(4) the main body of the cell casing has the side wall of an arc shape or an elliptic arc shape at both end of said major axis, that is the arc-shaped side wall, wherein each of the cells is arranged in a manner that
supposing that a section including the major axis of the lid wall and the major axis of the bottom wall is an imaginary sectional surface C, when disposing the arc-shaped side wall of each of the cells toward an arrangement reference surface D, firstly the imaginary sectional surface C is disposed so as to be inclined with respect to a vertical line which is perpendicular to the arrangement reference surface D. In this case, although the arrangement reference surface D represents a surface serving as a reference surface for arrangement when the cells are arranged in accordance with concrete conditions, the arrangement reference surface may be an actual surface on which a plurality of the cells are disposed thereon or on the side wall thereof. Further, when the arrangement reference surface D is an actual plane, the plane may be provided with a projection portion or a through hole.
Further, in the aforesaid cell arrangement method, it is preferable to dispose the arc-shaped side wall of each of the cells so as to be substantially made in contact with the arrangement reference surface D in order to house the cell within a limited space. In this respect, the expression xe2x80x9cdisposed to be substantially made in contact withxe2x80x9d means that the arrangement also includes a case where the arc-shaped side wall is slightly away from the xe2x80x9ccontactxe2x80x9d state within the range of the object of the present invention depending on the concrete conditions of the arrangement.
Further, in the aforesaid cell arrangement method, it is preferable to dispose the cells in a manner that the imaginary sectional surfaces C of the cells are substantially in parallel from one another in order to improve the spatial efficiency of the arrangement. Of course, such an arrangement includes a state where the imaginary sectional surfaces are not in parallel strictly, that is, a state where the imaginary sectional surfaces are substantially in parallel.
According to such an arrangement, the height of the cells at the time of the arrangement can be made small without changing the design of the cell.
Further, as a practically suitable arrangement method, it is preferable to dispose the cells in a manner that the lid walls or the bottom walls thereof are aligned on the same plane. According to such an arrangement, the terminals of the cells can be coupled easily from one another and the volume efficiency of the cells can be improved.
In the aforesaid arrangement, further, the cells are disposed with a space therebetween and the spaces among the plurality of cells form fluid paths, whereby coolant can pass through the spaces.
In this case, the cells of an elliptic cylindrical shape are disposed at a position into which coolant flows along the arrangement reference surface D, and an angle between the imaginary sectional surface C of the direction where the cells are disposed and the arrangement reference surface D of the direction from the coolant flows in forms an obtuse angle, whereby the resistance to the coolant when flowing among the cells can be made small and the cooling efficiency of the cells can be improved.
Furthermore, in the assembled battery formed by a plurality of cells of an elliptic cylindrical shape for solving the aforesaid problem, the cells are housed within an external casing using one of the aforesaid arrangement methods.
According to the present invention, the height of the cells at the time of the arrangement can be made small easily without changing the design of the cells, and further the arrangement suitable for passing the coolant can be realized.